The present invention relates to energy management systems used in vehicles, such as headliners, and to a process used to manufacture them.
In today""s automotive vehicle""s, energy management is an important consideration in protecting the occupants of a vehicle from injury in the event of a crash. As such, today""s automotive vehicles typically include energy management systems in their interiors that manage the energy resulting from an occupant contacting them in a crash. As used herein, xe2x80x9cenergy management systemxe2x80x9d means a structure that has a substrate bonded to an energy absorbing pad or crash pad, such as a honeycomb structure. Such energy management systems are incorporated in headliners, A-pillars, B-pillars, C-pillars, instrument panels, side door trim panels, bumper, glove boxes and knee bolsters. For example, one type of headliner 10, an exploded view of which is shown in FIG. 1, is made of a layer 12 of polyurethane or polypropylene foam having a polyester or polypropylene backing sheet 14 and a front sheet 16 of fabric presenting a good appearance, such as felt, for the surface that is visible when the part is installed in a vehicle (referred to herein as the visible surface). In the context of automotive applications, the visible surface of a part is referred to as the xe2x80x9cClass Axe2x80x9d surface. Polyester/polypropylene backing sheet 14 and front sheet 16 are typically bonded to polyurethane/polypropylene foam layer 12 by adhesive. Crash pads, such as polypropylene honeycomb structures, polypropylene rib structures, or other crash pad structures, are then bonded to the headliner at the appropriate locations. FIG. 2 is an exploded view of such a headliner/crash pad energy management system in which crash pads 18 are bonded to headliner 10 by adhesive as discussed below. In the resulting headliner/crash pad energy management system, the headliner is the substrate and the crash pad is the polypropylene honeycomb structure, polypropylene rib structure, or other crash pad structure.
Heretofore, energy management systems have been manufactured by bonding the substrates to their crash pads with adhesive. With reference to headliners and FIG. 1, a typical manufacturing sequence is to load the headliner 10 onto a fixture in a press. Adhesive is then applied to headliner 10. After the adhesive is applied, crash pads 18 are placed onto the adhesive on headliner 10 and the press closed. After an appropriate hold or cure time, the press is opened and the completed headliner/crash pad energy management system is removed
The foregoing process has a number of disadvantages. Adhesive guns are typically used to apply the adhesive to the substrate and they may leave excess adhesive or strings of adhesive on the backing and the visible surface of the substrate. An insufficient cure time and insufficient adhesive location may result in a weak bond between the substrate and the crash pad. Improper location of the crash pad on the substrate may result in interferences when the substrate/crash pad energy management system is installed in the vehicle. Further, the glue adds cost to the energy management system.
An energy management system in accordance with an embodiment of the invention has a substrate and a crash pad that are vibration welded together. In an embodiment, the substrate and crash pad are made at least in part of thermoplastic material. In an embodiment, the crash pad is a polypropylene honeycomb structure. In an embodiment, the crash pad is a polypropylene rib structure.
In an embodiment, the crash pad has a base layer of thermoset material, such as polyurethane, and a backing layer made at least in part of thermoplastic material, the crash pad and substrate being vibration welded so that the backing layer of the crash pad is vibration welded to the substrate. In an embodiment, the substrate has a backing layer made at least in part of thermoplastic material, the crash pad and substrate being vibration welded so that the backing layer of the substrate and the crash pad are vibration welded together. In an embodiment, the crash pad and the substrate can each have a backing layer made at least in part of thermoplastic material, the crash pad and substrate vibration welded so that their backing layers are vibration welded together.
In an embodiment, a headliner energy management system has a headliner having a base layer and a polyester or polypropylene backing layer, and a crash pad. The headliner and crash pad are vibration welded so that the polyester or polypropylene backing layer and crash pad are vibration welded together.
In an embodiment, a method for vibration welding first and second parts made of materials that are incompatible with being vibration welded includes prior to vibration welding the first and second parts, adhering to a surface of at least the first part a layer of material that is compatible with being vibration welded to the second part. In an embodiment, this layer of material is made at least in part of thermoplastic, such as polypropylene film. In a variant of the inventive method, respective layers of material that are compatible with being vibration welded to each other are adhered to surfaces of the first and second parts prior to the first and second parts being vibration welded. The first and second parts are vibration welded so that the respective layers of material on their surfaces are vibration welded together.
In an embodiment, a structure, such as an energy management system, is made by sandwiching a polypropylene honeycomb structure or polypropylene rib structure between polypropylene base plates. The polypropylene honeycomb structure or polypropylene rib structure is vibration welded to one of the polypropylene base plates and then vibration welded to the other polypropylene base plate.